EP1118842B1 - Air meter - Google Patents

Air meter Download PDF

Info

Publication number
EP1118842B1
EP1118842B1 EP20010100126 EP01100126A EP1118842B1 EP 1118842 B1 EP1118842 B1 EP 1118842B1 EP 20010100126 EP20010100126 EP 20010100126 EP 01100126 A EP01100126 A EP 01100126A EP 1118842 B1 EP1118842 B1 EP 1118842B1
Authority
EP
Grant status
Grant
Patent type
Prior art keywords
circuit
reference voltage
current
temperature
flow rate
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
EP20010100126
Other languages
German (de)
French (fr)
Other versions
EP1118842A1 (en )
Inventor
Masuo Akamatsu
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hitachi Ltd
Original Assignee
Hitachi Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Grant date

Links

Images

Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01FMEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through the meter in a continuous flow
    • G01F1/68Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through the meter in a continuous flow by using thermal effects
    • G01F1/696Circuits therefor, e.g. constant-current flow meters
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01FMEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through the meter in a continuous flow
    • G01F1/68Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through the meter in a continuous flow by using thermal effects
    • G01F1/696Circuits therefor, e.g. constant-current flow meters
    • G01F1/6965Circuits therefor, e.g. constant-current flow meters comprising means to store calibration data for flow signal calculation or correction

Description

    BACKGROUND OF THE INVENTION
  • This invention relates to an air meter, particularly to an air meter for measuring air mass flow suitable for the use of engine control for an automobile.
  • As the prior art air meter, a ratio-metric output type air meter is known having an output characteristic adjusting circuit and a ratio-metric converting circuit, as shown in JP10148556 . Also, in a frequency output type air meter, a ratio-metric output type air meter is known having an output characteristic adjusting circuit and a voltage controlled oscillator circuit.
  • However, in both of the ratio-metric output type air meter and the frequency output type air meter, two circuits of the respective air meters have independent internal reference power supply circuits, and to assure their accuracy it is necessary that a resistor is connected to the external of a monolithic IC, and therefore, it is necessary that the IC has connection terminals of the number proportional to the number of the internal reference power supply circuit outputs.
  • SUMMARY OF THE INVENTION
  • An object of this invention is to provide an air meter in which in case where a plurality of internal reference power supply circuits are needed, it is possible to improve the accuracy of the internal reference voltage with fewer IC terminals.
  • The above-mentioned and other objects of this invention can be attained by an air meter according to claim 1. It contains a characteristic adjusting circuit for adjusting the characteristic of a flow rate signal detected by flow rate detecting means, by using a first internal reference voltage, and outputting the flow rate characteristic signal, a conversion circuit converting the flow rate characteristic signal which this characteristic adjusting circuit outputs, to a ratio-metric output or a frequency output on the basis of a second internal reference voltage, and a reference power supply circuit for said first and second internal reference voltages, said internal reference power supply circuit comprising: a temperature current generating circuit for generating a current proportional to a temperature; a current mirror circuit for duplicating the current of this temperature current generating circuit, in that a first and a second current are created; a first reference voltage generating circuit through which said first current flows and which is arranged to generate said first reference voltage; and a second reference voltage generating circuit through which said second current flows and which is arranged to generate said second reference voltage.
  • With this arrangement, it is possible to improve the precision of the internal reference voltages with few terminal of IC.
  • In accord with another aspect of this invention, preferably said temperature current generating circuit uses as a resistor a thick-film resistor, and said first and second reference voltage generating circuits use a monolithic resistor and a thick-film resistor, respectively.
  • With this arrangement, it is possible to correct the linearity of the temperature characteristics of the reference voltages.
  • BRIEF DESCRIPTION OF THE DRAWINGS
    • Fig. 1 is a circuit diagram of an air meter according to a first embodiment of this invention;
    • Fig. 2 is a circuit diagramof an air meter according to a second embodiment of this invention; and
    • Fig. 3 is a circuit diagramof an airmeter according to a third embodiment of this invention.
    DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • Hereinafter, the arrangement of an air meter according to a first embodiment of this invention will be explained using Fig. 1. The explanation is given by exemplifying a ratio-metric output type air meter.
  • A flow rate detecting circuit 3 comprises a heat generating resistor 1 positioned in an air flowing path, and a constant temperature controlling circuit 2. The heat generating resistor 1 receives a current from the constant temperature controlling circuit 2, and is heat-controlled by self heat generation. The constant temperature controlling circuit 2 detects an air flow rate from the magnitude of heat current by controlling the heat current to maintain the resistance of the heat generating resistor 1 to a predetermined value, and generates a flow rate detection signal V2.
  • An output characteristic adjusting circuit 4 adjusts the characteristic of the flow rate detection signal V2 by adjusting a zero point and an amplification factor on the basis of Equation (1), thereby to generate a flow rate characteristic signal V4 by adjusting the output signal of the air meter to a predetermined characteristic. In order to adjust the zero point of the output characteristic adjusting circuit 4, an internal reference voltage ES generated by a band gap reference power supply circuit 6 is used. V 4 = K 1 × V 2 - K 2 × ES
    Figure imgb0001

    In this Equation (1), K1 is a constant for adjusting the amplification factor and K2 is a constant for adjusting the zero point.
  • A multiplication circuit 5 constituting a ratio-metric conversion circuit compares the internal reference voltage VINT generated by the band gap reference power supply circuit 6 with an external reference voltage VREF supplied from an engine control unit connected to the air meter, and converts the flow rate characteristic signal V4 created by the output characteristic adjusting circuit 4 to a ratio-metric characteristic on the basis of Equation (2), thereby to output an output signal VOUT from the air meter. VOUT = K 3 × V 4 × VREF / VINT
    Figure imgb0002

    In this Equation (2), K3 is a constant.
  • The engine control unit not shown in the drawings includes an AD converter for converting the signal of the air meter to a digital signal to control the engine using the signal of the air meter.
  • Now, Equation (2) can be expressed as following Equation (3) using Equation (1). VOUT = K 1 × V 2 - K 2 × FS × K 3 × VREF / VINT
    Figure imgb0003
  • From Equation (3), it is clear that since the internal reference power supply voltage ES causes the zero point to change and the internal reference voltage VINT causes the amplification factor to change, the internal reference power supply voltage ES and the internal reference voltage VINT are, if they are of independent characteristics, suitable to adjust the temperature characteristic of the air meter.
  • Therefore, in this embodiment, a semiconductor integrated circuit is effectively arranged by using a band gap reference power supply circuit 6 as means for generating the internal reference voltages ES and VINT.
  • Since any dispersion of the band gap reference power supply circuit 6 depends upon the dispersion of the transistors and resistors constituting it, the use of external resistors such as thick-film resistors formed on a circuit substrate on which an IC is mounted is suitable rather than the use of monolithic resistors integrated within an IC, because the dispersion of resistances and voltages is small. However, the former produces the problem that the number of terminals of the IC for connecting the transistors within the IC to the external resistors is increased.
  • Accordingly, in the band gap reference power supply circuit 6 according to this embodiment, a temperature current IT of which current value is proportional to the absolute temperature is generated by a temperature current generating circuit 21, and two internal reference voltages ES and VINT are generated by supplying temperature currents duplicated by a current duplicating circuit 22 to a reference voltage generating circuit 23 and a reference voltage generating circuit 24.
  • The reference voltage generating circuits 23 and 24 each comprises respective diodes or transistors and a respective resistor as shown in the drawing. In these arrangement, since the temperature characteristic of the forward voltage-drop voltage VF of the diode connection is negative with respect to temperature change, if it is added to the voltage drop of the resistor through which the current proportional to a temperature is flowed, it is possible to counterbalance any temperature change. Thus, it is possible to generate a reference voltage of which value does not change even though there is any change of temperature.
  • As explained above, in this embodiment, it is possible to provide a plurality of high precision band gap reference power supply circuit of which characteristic can be set up independently, with few IC terminals, rather than two integrated reference power supply circuits.
  • Next, the arrangement of an air flow rate meter according to the second embodiment of this invention will be explained. This embodiment will be explained using the example of a ratio-metric output type air flow rate meter.
  • Fig. 2 is a circuit diagram showing the arrangement of the air flow rate meter according to the second embodiment of this invention. Incidentally, the same reference numerals as those in Fig. 1 indicate the same parts or components.
  • In Fig. 2, a flow rate detecting circuit 3, an output characteristic adjusting circuit 4 and a multiplier circuit 5 are the same as the corresponding ones in Fig. 1.
  • A band gap reference circuit 6A comprises a temperature current generating circuit 21A, a current duplicating circuit 22, a reference voltage generating circuit 23A and a reference voltage generating circuit 24A.
  • The temperature current generating circuit 21A is made up transistors 25 and 26. The emitter of the transistor 25 is connected to a terminal 50, and the emitters of the transistors 26 is connected to a terminal 37. To these terminals, temperature currents IT of which values are proportional to the absolute temperature are supplied. The terminal 37 is connected to an external resistor 27 such as a thick-filmresistor, and the terminal 50 is connected to the external ground potential. The current duplicating circuit 22 is the same as the corresponding one of the Fig. 1.
  • The reference voltage generating circuit 23A comprises series-connected transistors 28 and 29, and resistors 30 and 31. The resistors 30 and 31 are connected to a terminal 39 for connecting thereto an external resistor. The resistor 30 is a monolithic resistor and the resistor 31 is a thick-film resistor which is the external resistor. The reference voltage generating circuit 23A has the output which is connected to an external connection terminal 40 through a voltage follower 36 to supply the reference voltage ES to the output characteristic adjusting circuit 4. Also, the reference voltage generating circuit 24A comprises series-connected transistors 32 and 33 and resistors 34 and 35 of which interconnections act as a terminal 38 to which an external resistor is connected. The resistor 34 is a monolithic resistor and the resistor 35 is a thick-film resistor which is the external resistor.
  • The band gap reference circuit 6A has the almost components housed within an IC and has four terminals 37, 38, 39 and 50 to which external resistors such as thick-film resistors are connected. Therefore, it is possible to use as the resistors as used in the reference voltage generating circuits 23A and 24A the combination of the external thick-film and inside IC monolithic resistors, and to correct the linearity of the temperature characteristic of the reference voltage. In the arrangement in Fig. 2, since it is possible to set up independently the amounts of correction for the linearity of the reference voltages ES and VINT with the ratio of the monolithic resistor 30 and the external resistor 31 and the ratio of the monolithic resistor 34 and the external resistor 35, the zero point of the air meter and the temperature of the span as well as the temperature characteristic linearity of the zero point and the temperature characteristic linearity of the span, respectively, can be adjusted to their respective optimum values.
  • Also, in the example shown in Fig. 2, since the internal of the IC and the terminal for providing the connection to the external resistors are connected using few number of terminals such as four terminals 37, 38, 39 and 50, it is possible to decrease the number of the IC connection terminal, and assure the accuracy of the band gap reference power supply circuit.
  • Next, the arrangement of an air meter according to the third embodiment of this invention will be explained using Fig. 3. This embodiment will be explained using a frequency output type air flow rate meter.
  • Fig. 3 is a circuit diagram showing the arrangement of the air flow rate meter according to the third embodiment of this invention. The reference numerals as used which are the same as those in Fig. 1 identify the same parts or components.
  • In Fig. 3, a flow rate detecting circuit 3 and an output characteristic adjusting circuit 4 are the same as the corresponding ones of Fig. 1. The multiplier circuit 5 as used in Fig. 1 is replaced with a VCO (voltage controlled oscillator) circuit 7. The VCO circuit 7 converts the output voltage signal V4 of the output characteristic adjusting circuit 4 to a frequency signal, and generates the output signal VOUT of the frequency output type air flow rate meter.
  • The band gap reference power supply circuit 6 generates an internal reference voltage ES for the output characteristic adjusting circuit 4 and an internal reference voltage VINT for the VCO circuit 7. Just like the case of Fig. 1, the band gap reference power supply circuit 6 comprises a temperature current generating circuit 21, a current duplicating circuit 22 and reference voltage generating circuits 23 and 24. The temperature current generating circuit 21 generates an temperature current IT of which value is proportional to the absolute temperature, and generates two internal reference voltages ES and VINT by supplying temperature currents duplicated by using the current duplicating circuit 22 to the reference voltage generating circuit 23 and the reference voltage generating circuit 24, respectively.
  • The reference voltage generating circuits 23 and 24 each is made up two diodes or transistors and a resistor as shown in the drawing. Since the temperature characteristic of the forward voltage-drop voltage of the diode connection is negative with respect to any temperature change, if the voltage drop due to the resistor through which the current proportional to the temperature is flowed is added to it, it is possible to cancel any temperature change and to generate a reference voltage of which value does not change depending upon the temperature change, using a selected resistor.
  • As explained above, in this embodiment, it is possible to provide a plurality of high precision band gap reference power supply circuit of which characteristic can be set up independently, with few IC terminals, rather than two integrated reference power supply circuits.
  • In accordance with this invention, in an air meter in which a plurality of internal reference power supply circuits are needed, it is possible to improve the degree of accuracy of an internal reference voltage with few IC terminals.

Claims (2)

  1. An air meter containing
    a flow rate detecting means (3),
    a characteristic adjusting circuit (4) arranged to adjust the characteristic of a flow rate signal V2 detected by said flow rate detecting means (3) by adjusting a zero point and an amplification factor using a first internal reference voltage ES, and outputting a flow rate characteristic signal V4,
    a conversion circuit (5) arranged to convert the flow rate characteristic signal V4 to a ratiometric output or a frequency output VOUT of the air meter on the basis of a second internal reference voltage VINT, and
    a reference power supply circuit (6) for providing said first and second internal reference voltages, characterized in that said internal reference power supply circuit (6) comprises
    a temperature current generating circuit (21) for generating a current proportional to a temperature;
    a current mirror circuit (22) for duplicating the current of this temperature current generating circuit (21), in that a first and a second current are created;
    a first reference voltage generating circuit (23) through which said first current flows (22) and which is arranged to generate said first reference voltage ES; and
    a second reference voltage generating circuit (24) through which said second current flows and which is arranged to generate said second reference voltage VINT.
  2. An air meter according to claim 1 wherein said temperature current generating circuit (21) uses a thick-film resistor (27) as a resistor include in said temperature current generating circuit (21), and said first and second reference voltage generating circuits (23, 24) include a monolithic resistor (30, 34) and a thick-film resistor (31, 35), respectively.
EP20010100126 2000-01-21 2001-01-12 Air meter Active EP1118842B1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
JP2000013370 2000-01-21
JP2000013370A JP3470073B2 (en) 2000-01-21 2000-01-21 Air flow meter

Publications (2)

Publication Number Publication Date
EP1118842A1 true EP1118842A1 (en) 2001-07-25
EP1118842B1 true EP1118842B1 (en) 2008-01-09

Family

ID=18540969

Family Applications (1)

Application Number Title Priority Date Filing Date
EP20010100126 Active EP1118842B1 (en) 2000-01-21 2001-01-12 Air meter

Country Status (4)

Country Link
US (2) US6691568B2 (en)
EP (1) EP1118842B1 (en)
JP (1) JP3470073B2 (en)
DE (2) DE60132263T2 (en)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3808038B2 (en) 2003-01-14 2006-08-09 株式会社日立製作所 Frequency output type hot-wire flow meter
JP4515828B2 (en) * 2004-06-02 2010-08-04 日立オートモティブシステムズ株式会社 Heating resistor type air flow meter
CN101419493B (en) 2007-10-25 2012-06-20 鸿富锦精密工业(深圳)有限公司 Fan running monitoring device
JP5304766B2 (en) * 2010-10-26 2013-10-02 株式会社デンソー Flow rate measuring device

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3060607B2 (en) 1991-07-08 2000-07-10 株式会社デンソー Hot-wire flow meter
JP2677923B2 (en) 1991-12-06 1997-11-17 株式会社日立製作所 Heating resistor type air flow meter
JP2846613B2 (en) 1996-02-28 1999-01-13 株式会社日立製作所 Pulse output type hot-wire air flow meter
DE19629747C2 (en) * 1996-07-23 1998-07-30 Siemens Ag sensor device
JP3300615B2 (en) * 1996-11-19 2002-07-08 株式会社日立製作所 Ratiometric output type heating resistor type air flow meter and the heating resistor type air flow meter and the engine control device
DE19818315C1 (en) * 1998-04-23 1999-09-16 Siemens Ag Radiometric sensor signal measuring device
JP3385995B2 (en) * 1999-03-01 2003-03-10 日本電気株式会社 Overcurrent detection circuit and a semiconductor integrated circuit with a built-in this
US6361207B1 (en) * 1999-06-04 2002-03-26 Florida Rf Labs, Inc. Temperature sensing termination

Also Published As

Publication number Publication date Type
JP3470073B2 (en) 2003-11-25 grant
EP1118842A1 (en) 2001-07-25 application
DE60132263T2 (en) 2009-01-02 grant
JP2001201382A (en) 2001-07-27 application
US6691568B2 (en) 2004-02-17 grant
US20030192378A1 (en) 2003-10-16 application
US20010009109A1 (en) 2001-07-26 application
DE60132263D1 (en) 2008-02-21 grant
US7040159B2 (en) 2006-05-09 grant

Similar Documents

Publication Publication Date Title
US5982221A (en) Switched current temperature sensor circuit with compounded ΔVBE
US6608472B1 (en) Band-gap reference circuit for providing an accurate reference voltage compensated for process state, process variations and temperature
US6229286B1 (en) Charging controller
US5814995A (en) Voltage detector for battery operated device
US5394078A (en) Two terminal temperature transducer having circuitry which controls the entire operating current to be linearly proportional with temperature
US7173407B2 (en) Proportional to absolute temperature voltage circuit
US5774013A (en) Dual source for constant and PTAT current
US5589759A (en) Circuit for detecting voltage variations in relation to a set value, for devices comprising error amplifiers
US4516865A (en) Resistance thermometer
US4958520A (en) Digital piezoresistive pressure transducer
US6037833A (en) Generator for generating voltage proportional to absolute temperature
US5559500A (en) Overcurrent sense circuit
US20060197581A1 (en) Temperature detecting circuit
US20080074172A1 (en) Bandgap voltage reference and method for providing same
US4487063A (en) Solid state mass air flow sensor
US4475077A (en) Current control circuit
US7204638B2 (en) Precise temperature sensor with smart programmable calibration
US6198296B1 (en) Bridge sensor linearization circuit and method
US6956727B1 (en) High side current monitor with extended voltage range
US4362060A (en) Displacement transducer
US5945853A (en) Current sensing circuit with automatic offset compensation
US6373330B1 (en) Bandgap circuit
US20090256623A1 (en) Temprature sensor circuit
US5166550A (en) Comparator circuit with variable hysteresis characteristic
US20090201067A1 (en) Reference voltage generating circuit, integrated circuit device, and signal processing apparatus

Legal Events

Date Code Title Description
AX Request for extension of the european patent to

Free format text: AL;LT;LV;MK;RO;SI

AK Designated contracting states:

Kind code of ref document: A1

Designated state(s): DE FR GB

17P Request for examination filed

Effective date: 20011120

AKX Payment of designation fees

Free format text: DE FR GB

17Q First examination report

Effective date: 20060726

RAP1 Transfer of rights of an ep published application

Owner name: HITACHI, LTD.

AK Designated contracting states:

Kind code of ref document: B1

Designated state(s): DE FR GB

REG Reference to a national code

Ref country code: GB

Ref legal event code: FG4D

REF Corresponds to:

Ref document number: 60132263

Country of ref document: DE

Date of ref document: 20080221

Kind code of ref document: P

ET Fr: translation filed
26N No opposition filed

Effective date: 20081010

PGFP Postgrant: annual fees paid to national office

Ref country code: FR

Payment date: 20130204

Year of fee payment: 13

Ref country code: GB

Payment date: 20130109

Year of fee payment: 13

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 20140112

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

Effective date: 20140930

PG25 Lapsed in a contracting state announced via postgrant inform. from nat. office to epo

Ref country code: FR

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20140131

Ref country code: GB

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20140112

PGFP Postgrant: annual fees paid to national office

Ref country code: DE

Payment date: 20180103

Year of fee payment: 18